The present invention relates to an improved electrophotographic photoconductor comprising an electroconductive support, an intermediate layer formed on the support which is capable of preventing charge injection from the electroconductive support to a photoconductive layer and a photoconductive layer formed on the intermediate layer.
A variety of trials have been made with an object of providing conventional electrophotographic photoconductors comprising a substrate and an electrophotographic photoconductor formed thereon, in particular, layered-type electrophotographic photoconductors comprising a substrate and an electrophotographic photoconductive layer consisting of a charge generating layer and a charge transporting layer, with a high chargeability, a high photosensitivity and a low residual potential. In one of such trials, it has been proposed to interpose an intermediate layer between an electroconductive support and a charge generating layer of a photoconductive layer, which intermediate layer functions to prevent the injection of electric charge with a polarity opposite to the charging polarity of the photoconductor from the electroconductive support to the charge generating layer. More specifically, intermediate layers made of cellulose nitrate resins are disclosed in Japanese Laid-Open Patent Applications Nos. 47-6341, 48-3544 and 48-12034; intermediate layers made of polyamide resins in Japanese Laid-Open Patent Applications Nos. 48-47344, 52-25638, 58-30757, 58-63947, 58-95351, 58-98739, 60-66258 and 61-110153; an intermediate layer made of vinyl acetate resin in Japanese Laid-Open Patent Application No. 48-26141; intermediate layers made of maleic acid resin in Japanese Laid-Open Patent Applications Nos. 49-69332 and 52-10138; and an intermediate layer of polyvinyl alcohol resin in Japanese Laid-Open Patent Application No. 58-105155.
The electrophotographic photoconductors including such intermediate layers, however, have the shortcomings that when they are used in repetition, the rising rate of the surface potential at the time of the charging of the photoconductors is small, the charging characteristics and obtained image density deteriorate with time, and toner is apt to be deposited on the background of images at the time of reverse development.